Subdomain Enumeration

Posted by Zaid Sabih
Date July 10, 2025

What is Subdomain Enumeration?

The process of identifying subdomains associated with a main domain to map attack surfaces.

Expanded Explanation

Subdomains may reveal development environments, staging servers, or APIs. Tools like Sublist3r, Amass, and crt.sh are frequently used in OSINT workflows.

Related Terms

DNS Records, Domain Footprinting, Reconnaissance, Attack Surface, Web Recon.

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Zaid Sabih

Ethical Hacker, Pentester & Computer Scientist

Zaid Al-Quraishi is an ethical hacker, computer scientist, and founder of zSecurity. He studied CS at UCD, graduating May 2016.

Zaid has a strong background and experience in ethical hacking, starting with tutorials in 2009 in an ethical hacking community, iSecur1ty. He also worked as a penetration tester (pentester) for this company.

In 2013 he started teaching his first course online in Arabic which received extremely positive feedback. This motivated him to create an English version of the course. The English course became the most popular and top paid course on Udemy for almost a year, which further motivated Zaid to design and teach more courses on ethical hacking.

He now offers a number of courses on ethical hacking and more than 800,000 students on Udemy and other teaching platforms such as StackSocial, StackSkills and zSecurity.

Zaid says: "I just love hacking and breaking the rules but don't get me wrong, I am an ethical hacker!"

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